A navigation system for use in a vehicle conventionally determines a destination of a travel by detecting a length of stopping time at a certain place. For example, the navigation system disclosed in Japanese patent document JP-A-2001-50760 uses a stoppage detection unit for detecting a stoppage of the vehicle, and determines whether the time of the stoppage is longer than a predetermined time by using a control unit. The stoppage of the vehicle is recorded as a parking history in a SRAM memory with the attributes of stopping location and other information. In this manner, the destination of the travel can be selected from entries in the parking history by a user of the navigation system. The user can search and pick up the destination in the history by inputting a search condition or other attributes.
The navigation system disclosed in Japanese patent document JP-A-H11-153446 records an accumulative travel history including a start/end location of a travel, date and time of the travel, and a distance of the travel based on the detected vehicle condition. The navigation system searches the accumulative travel history for calculating statistics such as a travel destination distribution and a travel time distribution for the most frequented travel destination based on the date and time of the travel when the navigation system is turned on at the start of the travel. Then, the destination of the travel predicted by the navigation system with an estimated travel time is announced from the navigation system. In addition, the navigation system in this disclosure determines that the vehicle has reached the destination of the travel based on the assumption that an ignition key of the vehicle is pulled out from the ignition switch at the destination of the travel.
The navigation systems disclosed in the above-described patent documents determine that the vehicle has reached the destination of the travel by detecting the period of the stay or by detecting that the ignition key is pulled out. However, the user of the vehicle does not necessarily keep the vehicle for a period longer than the predetermined time nor pull out the ignition key from the ignition switch. For example, the user of the vehicle sometimes stops at a facility, a restaurant or other place on his/her way to the destination for various reasons such as taking a rest, having a meal or the like. In this case, the vehicle may stop at those places for a period longer than the predetermined time, or the user may pull out the ignition key from the ignition switch at those places.
The stop-by places on the way to the destination of the travel detected and determined based on the above-described assumptions may cause inconvenience for the user if the stop-by places are recorded as the destination of the travel for later use. That is, the destinations of the travel based on the accumulative travel history recorded by the navigation system may not provide “real” destinations because of the inaccuracy of the accumulated travel history.